Advantages of conditional-preprocessor over conditional statements

Question

I have never worked with #if, #ifdef, #ifndef, #else, #elif and #endif

Answer 1

The example you showed doesn't seem helpful due to lack of other information. But here's an example that #if is useful.

#if OS == LINUX
//do something
#elif OS == SOLARIS
//do something else
#else
//
#endif

The key is that #if is evaluated in compile time, but if is evaluated when program runs.

#if BYTE_ORDER == LITTLE_ENDIAN
//do something
#else
//do something else
#endif